Most tumors include associated antigens that are capable of inducing an immune response in their hosts. Despite this immune response, tumors generally continue to grow in vivo. The presence of circulating immune complexes in the plasma of tumor hosts has suggested one possible explanation to this paradox. Although the role of circulating immune complexes remains uncertain, it has been established that Staphylococcus Protein A (SPA), a molecule found in the wall of certain strains of Staphylococcus aureus, can adsorb the circulating immune complexes in the plasma of tumor bearing hosts.
Previous techniques for bringing a host's blood into contact with SPA have involved removing blood from the host, separating the removed blood into plasma and cellular components, and bringing the plasma into contact with heat-killed Staphylococcus aureus, or with a collodion-charcoal support to which SPA was mechanically bound. All such techniques have been found to produce significant undesirable side effects in human patients. The use of a collodion-charcoal support possesses the further disadvantages that only minute amounts of SPA can be mechanically bound to such a support, and that SPA rapidly leaches off the support during use.